lighting tip sheet (v-2.0 march 2011)
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Lighting is a major energy consumer in commercial buildings. Heat generated from electrical lighting also contributes signicantly to the energy needed for
cooling of buildings. ECBC prescribes the amount of power for lighting, species
types of lighting controls, and denes situations where daylighting must be used.
This document (primarily adapted from E Source Technology Atlas - Lighting
and Energy Eciency Manual) provides guidance towards the design of ECBC
compliant lighting systems in commercial buildings.
ENERGY CONSERVATION
BUILDING CODE TIP SHEET
Version 2.0- March 2011
BUILDING LIGHTING DESIGN
Credits:
E Source echnology Atlas Series - Lighting
Energy Efficiency Manual - Donald R. Wulfinghoff
All iance to Save Energy
USAID ECO-III Project
International Resources Group
Phone: +91-11-4597-4597
Fax: +91-11-2685-3114
Email: [email protected]
In commercial buildings,
lighting typically accounts or 20-40% o total energy consumption.
Lighting is an area that oers manyenergy eiciency opportunities in almostany building, existing as well as new. Atypical commercial building has manylighting requirements and each normallyhas its own set o options or improvinglighting eiciency.
Centuries ago, a person could read by
the light of a single candle but today aperson in a typical office uses hundredsor even thousand times more light. Over
1
the years, illumination standards haveincreased radically along with efficiencyof lamps (Fig. 1). Modern offices requi rebetter illumination, specific activity-oriented lighting provisions, and goodvisual quality to maximize productivity.
People want light for different reasons,and a good lighting designer must keepthem in mind. Different tasks requiredifferent amounts and types of light. Forexample, a surgeon needs lots of light with
low glare and excellent color rendering;restaurant owners and diners often wantlow light levels, warm tones, and a feeling
of intimacy; corporate boardrooms callfor lighting that reinforces a feeling ofimportance and success while adapting toaudio-visual presentations; retail outletsin many situations want to make theirmerchandise sparkle so that it draws thecustomers and encourages them to buy.
An office worker needs modest ambientlighting level, good task lighting on worksurface, and minimal glare to effectivelyread and work on computers. Tus the
quality of light in majority of situationsis as important as the quantity of light. While energy efficiency is an
attractive goal for many reasons,lighting designers must also considera host of other factors, including theeffect of quality of light on the visualcomfort and health of the occupants.Small improvement in lighting qualitycan improve productivity of the usersubstantially.
he right quality and quantityof light can be provided efficiently
(with less energy) by using the righttechnology and its effective integration
with dayl ight.
12 lm/80 W
0.15 lm/W
7.5-hour life
730 lm/13 W
56 lm/W
10,000-hour life
Notes: lm = lumen; W = watt.
730 lm/60 W
12 lm/W
1,000-hour life
180 lm/60 W
3.0 lm/W
50- to 100-hour life
CandleC o m p a c t
fluorescent Tungs ten -fi lame nt
incandescent
Carbon-filament
incandescent
Fig 1: Evolution of Lighting Technologies
(Source: E Source Lighting Atlas)
CompactFlourescent
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Daylighting Sunlight is free and uses no electricity.Human beings by nature are accustomed tolive and work more comfortably in sunlight.
Although our optical sensors (humaneye) can only see a very narrow portion ofelectromagnetic spectrum, they are welladapted to sunlight (Fig. 2). Both economics
and the imperatives of health and aestheticsfavour the practical use of daylight in thebuildings. Simply adding a large numberof windows to a building to “let the sunshine in” can create excessive glare, makeother spaces look dark by contrast, andadmit so much unwanted heat gain due tonear infrared radiation that the space couldbecome virtually unusable.
Poorly designed daylit areas can be worsethan spaces with no daylight. Whendone properly, daylighting coupled
with energy-ef ficient glazing and good
lighting controls can make new andexisting buildings efficient, delightfuland healthy. he tools to do it rightexist, and are being applied by a growingbody of talented lighting designers.
Heating Effects of Lighting
Lamps use electricity to produce light.Except for a small percent of energy usedin producing light, majority of energy usedby interior lights ends up as heat inside thebuilding. In most commercial buildings,
lighting is one of the largest sources ofinternal heat gain. Other sources of internalheat gains are people and equipment inbuilding. Compared to typical lighting,energy-efficient lighting adds less heatto space per unit of light output. Eachkilowatt-hour (kWh) reduction in lightingenergy saves 0.4 kWh in cooling energy.
Lighting Technology
Lighting is one of the fastest developingenergy-efficient technologies: energy-efficient 8 and 5 linear fluorescent
lamps, linear and compact fluorescentdimming systems, long-life electrode lessf luorescent lamp systems, white LEDs,and PV powered DC lighting systems.
Fig 2: Solar Spectrum
(Source: E Source Lighting Atlas)
300 500 700 900 1,100 1,300 1,500 1,700 1,900
Near- infared
(52%)
Visible(45%)
UV(3%)
R e l a t i v e I n t e n s
i t y
Wavelength
(nanometers)
Spectral distribution of
Solar radiation
Eye Sensitivity
Curve
into account several human factors inspecifying lighting systems.
Lighting Design Tools
Lighting software helps designers tocompare lighting alternatives and makessure that the ultimate design choice
wi ll provide qua lity light. Demands
on lighting designs are becomingmore complex as both lighting qualityand energy efficiency have becomehigh priorities. In addition, a widerange of variables—different lightsources, fixtures of varying efficiencyand photometric, and rooms with a
wide range of geometries and sur facefinishes—all make lighting design achal lenge worthy of computer modeling.In particular, the trend among fixturemanufacturers to use specular reflectorsthat send light in particular directionsmakes modeling more useful than it was
with the old-sty le, white-painted diffusereflectors. Most computer models canalso simulate the effects of daylight andcan be used to help designers to developeffective control strategy for getting theoptimum blend of electric lighting anddaylighting.
Once constructed, a computer lightingmodel can be easily modified so that variousfixture designs and spacings can be evaluatedand compared in terms of horizontal and
vertical light levels. Designs that give properquality and quantity of lighting can beevaluated for their energy consumption,and the design that gives both the desiredlighting level and the lowest life-cycle costcan be selected. Output from lightingsoftware can also be input into software thatmodels an entire building to enable analysisof the impacts of lighting decisions on otherbuilding systems. Lighting professionals whodo not first model the design, face the risk ofgetting poor light distribution or more light
than they expect. Both the problems can bedifficult and expensive to correct.
Lamp Technologies
Incandescent Lamps An incandescent lamp consist s of atungsten wire filament that glows andproduces visible light when heated to ahigh temperature. Unfortunately, 90to 95 % of the power consumed by thehot filament is emitted as infrared (heat)radiation. Although inefficient from
an energy standpoint, the luminousfilament can be made quite small, thusoffering excellent opportunities forbeam control in a very small package.
Selection of lamp should be thestarting point when deciding how toilluminate a space efficiently. Lampsare also the primary actor in lightingefficiency, and they determine boththe electrical and color characteristicsof the lighting systems. When a lampis coupled with its auxiliary equipment
(e.g. a ballast or “choke”) and installedin a luminaire (fixture), it becomes thecomplete light source that is the basicelement of the lighting design.
It has long been recognized that anincandescent lamp is much less efficientthan fluorescent and High IntensityDischarge (HID) lamp, and that it hassmaller operating life. In recent years,further improvements in the efficiencyand color characteristics of fluorescentand HID lighting have increased theiradvantage over incandescent lighting.
Light Distribution
hough energy-efficient technologiescan cut down energy consumption andoperating costs, the light path originatingfrom the light source if not properlydirected and distributed to the task oractivity area through appropriate lampluminaires (fixtures), could adverselyaffect the quality of light and reduceenergy efficiency gains. Consequently,luminaire selection and design should
go together with any energy-efficientlighting strategy.
Lighting Controls
Controls are the last step in the energy-efficient lighting design process andshould be designed after high-efficiencylight sources have been chosen. hecontrollability of light sources varies
widely, with low-efficacy incandescentlamps being the easiest to control.echnological developments continue
to provide new control capabilities forfluorescent and HID systems.
Efficient Lighting Design
Optimal lighting solutions can only bereached by considering the integrationof daylight, lamps, fixtures, controls,building configurations, interiorfurnishing, etc. Ideal lighting providesthe appropriate level of illuminationfor the activity with minimum inputof energy, with required visual quality.For efficient lighting design, it is often
necessary to involve a skilled lightingdesigner who combines energy eff iciency
with good quantit y and qua lity of lightneeded for the activity and also takes
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For implementing the ECBC provisionsin lighting system, it is important tounderstand the ollowing technical terms:
Astronomical time switch: An automatictime switch that makes an adjustment or
the length o the day as it varies over the year.
Ballast: All fluorescent lamps need aballast to operate. Te primary unctionso a ballast are to provide cathode heating where necessar y, initiate the lamp arc with high-voltage, provide lamp operating power, and then stabil ize the arc bylimiting the electrical current to the lamp.Secondary unctions include input power-quality correction and control eaturessuch as lamp dimming or compensationor lumen depreciation.
Candela: It is a measure o the intensity(or brightness) o light source in a givendirection (Fig. 3).
Color Rendering Index (CRI): Measuredon a scale o 0 to 100. It specifies the colorrendition properties o a lamp. Te higherthe average CRI value, the better the lightsource. A cool white fluorescent lamp has aCRI o 62 to 70, 8 lamps range rom 75to 98 and standard high-pressure sodiumlamps have CRIs o about 27. Lamps withCRIs above 70 are typically used in officeand living environments.
Correlated Color Temperature (CCT):
A measurement on the Kelvin (K) scalethat indicates the warmth or coolness oa lamp’s color appearance. Te higher the
color temperature, the cooler or bluer thelight. ypically, a CC rating below 3200K is considered warm, while a rating above4000 K is considered cool.
Illuminance: Te amount o light that
reaches a surace. It is measured in ootcandles (lumens/f2) or lux (lumens/m2).
Installed interior lighting power: Te power in watts o all installed general,task, and urniture lighting systems andluminaires.
Lighting Power Allowance:
a) Interior lighting power allowance: themaximum lighting power in wattsallowed or the interior o a building
b) Exterior lighting power allowance:the maximum l ighting power in wattsallowed or the exterior o a building
Lighting Power Density (LPD): Telighting power drawn per unit o areao a building type or space. It is usuallyexpressed as watts per square meter or watts per square oot.
Occupancy Sensor: A device that detects
the presence or absence o people withinan area and causes lighting, equipment, orappliances to regulate their operation orunction accordingly.
Reflectance: Te ratio o the light reflectedby a surace to the light incident upon it.
Visible Light Transmittance: Also knowas the Visible ransmittance, is an optical property o a light transmitting material(e.g. window glazing, translucent sheet,
etc.) that indicates the amount o visiblelight transmitted o the total incidentlight.
Luminance: It measures the brightnesso a source when viewed rom a particulardirection. It is expressed in term ocandela/m2 o the light emitting surace.Luminance describes the intensity olight that is leaving a surace whereasilluminance describes the intensity olight that is alling on a surace. For lightreflected rom a surace, luminance equals
illuminance multiplied the reflectance othe surace.
Lumen: It is the unit i total light outputrom a light source o a lamp is surroundedby a transparent bubble; total light flowthrough the bubble is measured in lumens.Lamps are rated in lumens, which is thetotal amount o light they emit, not their
brightness and not the light level on asurace. ypical indoor lamps have lightoutput ranging rom 50 to 10,000 lumens.Lumen value is used or purchasing andcomparing lamps and their outputs.Lumen output o a lamp is not related tothe light distribution pattern o lamp.
Lux: It is the unit o illuminance andindicates the density o light that allson a surace. One lux equals one lumen per square meter o the surace while onelumen per square oot o the surace isequal to 1 oot-candle. One oot-candleequals 10.76 lux. Average indoor lightingrange rom 100 to 10,000 lux and averageoutdoor sunlight is almost 50,000 lux.Tese lumens and candela are measuredby special photometric instruments inlaboratories and are used primarily orcomparing light sources independento site conditions. Lux and oot-candlesare measured in the field with a meterand may be dependent on site conditionsbecause, unlike candelas or lumens, they
are influenced by fixture, room suracereflectance, partitions, and other actors.
Lamp Efficacy: Lamp Efficacy is ameasure o the output o a lamp in lumens,divided by the power drawn by the lamp.Its units are lumens per watt. Lampefficacy values are based exclusively on thelamp’s perormance and do not includeballast losses. Lamp system efficacy valuesmeasures the perormance o the lamp andballast combination and this includes the
ballast losses.
Light Luminaire (Fixture): A lightfixture, consists o the ballast, lamp,reflector, in some cases a lens, designed todistribute the light, position and protectthe lamps, and connect the lamps to the power supply.
T#: As in 5, 8, 12 fluorescent lamps. stands or tubular; the number describeslamp diameter in one-eighth-inchincrements. A 8 lamp is eight-eights o
an inch (or 1 inch) in diameter; a 12 istwelve-eighths o an inch (or 1.5 inches) indiameter.
A 1-candlepower light source delivers a luminous intensity of
1 candela (cd) in all directions. Assuming that the sphere has
a radius of 1 foot (ft), the light source will deliver 1 lumen (lm)
of light to each square foot (ft2) of surface of the sphere, so the
illuminance is 1 foot-candle (fc).
1cd
1cd
1-ft2”hole”
R a d i u
s = 1 f t
Illuminance
At any point onthis imaginary 1-ft-
radius sphere, the
illuminance equals
1 lm/ft2, or 1 fc.
Luminous
intensity = 1 cd
One candle power
luminous source
Light flow=1lm/ft2
Fig 3: Relationship of light measurement
terms
(Source: E Source Lighting Atlas)
Key Technical Terms
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are shown in able 1. Electronic ballasts, which have come to dominate the marketfor compact fluorescent lamps (CFLs), aremore efficient, weigh less, and are quieterthan magnetic ballasts.
Some argue that CFLs are such smallloads that their PF and HD should notbe o major concern, especially becausemany other end-use devices on the powergrid—personal computers, copiers, laser printers , microwave ovens , televisions,stereos, variable-speed motor controls,and others—also degrade power qualityin varying degrees and typically use armore power per unit.
Mercury is an essential ingredient formost energy-efficient lamps. Te amountof mercury in a CFL’s glass tubing is small,about 4mg. However, every lamp productcontaining mercury should be handled
with care. Fig. 6 puts mercury pollution
Linear and Compact FluorescentLamps (CFLs)he basic fluorescent lamp contains lowpressure mercury vapor and inert gasesin a partially evacuated glass tube thatare lined with phosphors (Fig. 4). CFLsoperate in the same manner as linearfluorescent lamps. he high surface
brightness of CFLs requires the use ofrobust rare earth phosphors, such asthose used in modern 8 and 5 linearfluorescent lamps, in order to provideacceptable lumen maintenance.
he efficacy (lumens per watt) offluorescent lamps varies considerably
with lamp wattage and ballast typeand quality (Fig. 5). he efficacy of a5-watt CFL on a low-quality magneticballast, for example, can be as low as27 lumens per watt (lm/W). At the
other extreme, two 36-watt compactf luorescent lamps powered by a singlehigh-quality electronic ballast delivernearly 77 lm/W. ypical incandescentlamps operate with an efficacy of 15 to18 lm/W, so even a low-efficacy CFLis significantly more efficient than theincandescent lamp it might replace.
CFLs have been substituted or anincandescent lamp using the rule othumb that a CFL uses only 20-25% power to deliver the same lig ht output.
However, but many manuacturers’ product literat ure exaggerates CFLperformance by “rounding up” whenidentifying the “equivalent” incandescentlamp. For example, a CFL may beadvertised as a replacement for a 75-watt,1,200-lm incandescent lamp, but it mayonly produce 1,000 lm. A more accuratedescription would put the light output ofa CFL midway between that of 60W and75W incandescent lamps.
Te effect of CFL on power quality hasbeen debated widely for several years. Te
two primary issues are the Power Factor(PF) and otal Harmonic Distortion(HD) of the ballasts. ypical PF andHD ranges for various ballast types
Notes: Hg = mercury; UV = ultraviolet
UV photon
Hg
Visible photon
Fluorescent lamps maintain an electric arc th roughgas, in contrast to the continuous metal ilamentsused in incandescent lamps.
Fig 4: Fluorescent lamp operation
(Source: E Source Lighting Atlas)
from the use of CFLs in a broader context(mercury pollution from thermal powerplants generating power). High Intensity Discharge LampsHID lighting sources are the primaryalternative to high-wattage incandescentlamps wherever an intense, concentratedsource of light is required. here arethree basic types of HID lamps: MercuryVapor, Metal Hal ide, and High-PressureSodium. Although HID lamps canprovide high efficacy, they have specialrequirements for start-up time, restriketime, safety, and mounting position.
a) Mercury-Vapor LampsMercury-vapor (MV) lamps use a high-pressure mercury discharge that directlygenerates visible light (Fig. 7). Someversions also use a phosphor coating on
Table 1: Magnetic and Electronic Ballasts Characteristics for
CFLs
Ballast Characteristics Magnetic Electronic
CFL base compatibility Mostly two-pin Mostly four-pin
Lamp/ballast efficacy Low High
Weight High Low
Noise level Slight 120-Hz hum Very quiet
Cost Cheaper Expensive
No. of lamps powered/ballast 1 or 2 1, 2, 3 or 4
Dimmability No Available
Universal input voltage No Available
Power Factor 0.4 to 0.7 (normal; > 0.9 (better)0.4 to 0.7 (normal; > 0.9 (better)
otal Harmonic Distortion (%) 6-18 (normal); 15-27 (better) 75-200 (normal); 16-42 (better)
Source: E Source Lighting Atlas
Fig 5: Relative efficacy of major light sources
(Source: E Source Lighting Atlas)
Standard incandescent
Tungsten halogen
Halogen infrared reflecting
Mercury vapor
Compact fluorescent 5–120 W
Low-pressure sodium
Efficacy, including ballasts
(lumens per watt)
Fluorescent (Linear and U-tube)
Metal halide
High-pressure sodium
0 20 40 60 80 100 120 140
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the inside of the outer bulb to convertthe small amount of ultraviolet (UV)light generated by the discharge intoadditional visible light that improves thecolor of the lamp. MV lamps have lowerefficacy than fluorescent lamps and otherHID lamps.
b) Metal-Halide LampsMetal-Halide (MH) lamps are similarto MV lamps but feature an importantimprovement: the addition of iodides ofmetals such as thallium, indium, andsodium to the arc tube. hese metalsproduce a higher quality and quantityof light than mercury, and the halidesform the basis of a regenerative cyclethat prevents the metal s from depositing
on the wall of the arc tube. MH lampstake three to five minutes to reach fulloutput. Restarting after a shutdown orpower interruption may require as much
its proponents. LEDs use solid-stateelectronics to create light. Majorelements in the packaging of an LEDinclude a heat sink to dissipate theenergy that is not converted into light, alens to direct the light output, and leadsto connect the LED to a circuit. Fig. 8shows a cross section of an LED fixture.
LEDs are increasing in efficacy, lightoutput, and color availability whiledropping in cost. High brightness,narrow-band, or various-color LEDsare being used increasingly in vehiclesignal lights, traffic signal lights, exitsigns, and decorative and informationdisplay applications. Composite units ofred, green, and blue LEDs, or of systemscomposed of a blue or violet LED plusa phosphor coating, are being used tocreate white light further expanding LEDapplications.
able 2 shows the comparativecharacteristics of different light sources.
Fixture & Reflector he full potential for energy-efficientlighting comes only through intelligentintegration of many system variables.hese range from the most minutedetails of lamp design through theblending of lamps, ballasts, reflectors,lenses, and other components.
It is not enough to select good lamps
and other components. However,one must also understand how thesecomponents behave in the field. In thelab, fluorescent lamps are typically ratedin open-air fixtures at 25°C ambienttemperature with a reference ballast thatdrives the lamp to its fu ll rated output. Inthe field, however, many ballasts underdrive or overdrive lamps. Te so-calledballast factor and the temperature of thelamps in field conditions can cause lightoutput to vary by 20 percent or more.Lamp position—whether it is installed
base up or base down—can also have a10 to 20 percent effect on light outputfrom certain sources, such as compactfluorescent lamps.
Fig 8: LED Operation
(Source: E Source Lighting Atlas)
Plastic lens
Silicone
encapsulate
InGaN
Semiconductor
Flip chip
Solder connection
Silicon submount chip with
ESD protectionHeatsink slug
Gold wire
Cathode lead
as 10 to 15 minutes for the arc tube tocool and the mercury and metal-halidegas densities to drop before the arc canbe restruck, plus another three to fiveminutes to reach full output again. MHlamps produce relatively high levels ofUV radiation that can be controlled withshielding glass in the lamp or fixture.
c) Sodium LampsIn sodium lamps, a high-frequency,high voltage pulse ionizes a rare gas,typically xenon, in an enclosed tube.he ionized gas in turn vaporizes asodium-mercury amalgam. An electric
arc through this vapor excites sodiumatoms, which emit visible light—mostlyin the longer wavelengths betweenyellow and red—when they return totheir ground state. For high-pressurelamps, the gas mixture is sealed in atranslucent polycrystalline aluminacylinder that transmits 90 percent of thevisible light created inside it. Sodiumlamps vary widely in their efficacy andcolor quality, and their performance isvery sensitive to the gas pressure inside
the arc cylinder. Improving the qualityof light from some sodium sources,significantly reduces their efficacy.
Light-Emitting DiodesDuring the past few years, solid-statelighting in general and Light EmittingDiodes (LEDs) in particular havereceived more attention than any otherlighting technology. his high level ofinterest is based on the demonstratedperformance advantages of LEDs inmany niche applications, and it is also
fueled by LEDs’ potential for substantialenergy savings in general lightingapplications if the technology can meetthe performance targets established by
Fig 7: Mercury Vapor Lamp Schematic
(Source: E Source Lighting Atlas)
Starting electrode
(probe)
Starting resistor
Trimetallic operating
electrode
Phosphor coating
Quartz arc tube
Visible light
2
2
33 Outer bulb
1
1 UV light
Electric
field
Electrode
Electron Mercury
atom
Quartz arc tube
As energy-efficient lighting becomesmore popular, it is important that thelamp products are disposed o in a saeand responsible way. Mercury is releasedinto environment when products with mercur y are broken, disposed oimproperly, or i ncinerated.
In spite of the sensational reporting inprint and electronic media, the fact is thatCFLs present an opportunity to preventmercury contamination of air, where itmost affects the health. One of the majorsources of mercury in air comes fromburning fossil fuels such as coal, the mostcommon fuel used in India to produceelectricity. A CFL uses 75% less energy
than an incandescent light bulb and lastssix times longer. A thermal power plantemits 10 mg of mercury to produce theelectricity to run an incandescent bulbcompared to only 2.4 mg of mercury torun a CFL for the same time.
Fig 6: Mercury Emissions by Light
Source Over Year Life
(Source: US EPA, June 2002)
12
10
8
6
4
2
0
Emissionsfrom coal
power point
IncandescentCFL
Emissions from coalpower plant
2.4
10.0
4.0 Mercury usedin CFL
M i l i g r a m s o f M e r c u r y
Environmental Impacts of Mercury Used in Fluorescent Lamps
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Table 2: Comparative Characteristics of Different Light Sources (Source: Energy Efficiency Manual)
CharacteristicsConventional
Incandescent
Halogen
Incandescent
Fluorescent
Tube Light Compact Fluorescentt
Lumen Output(lumens) 10 to 50,000
300 to 40,000 900 to 12,000 250 to 1,800
Lumen Degradation(% of initial lumens) 15 to 40 8 to 15 8 to 25 15 to 20
Service Life (hours) 750 to 4,000 2,000 to 6,000 7,000 to 20,000 10,000
Efficacy (lumensper watt)
7 to 22 14 to 22 30 to 90 25 to 70, Including ballast losses
Ballast EnergyConsumption (percentof lamp wattage)
None None5 (high quality electronicballasts) to 20 (cheapmagnetic ballasts)
10 (electronic ballasts) to20 (magnetic ballasts)
Potential for LampSubstitution andMismatch
Unlimited substitution wherever the lamp fits thefixture, provided that fixtureheat capacity is adequate.
Unlimited substitution wherever the lamp fitsthe fixture, providedthat fixture heatcapacity is adequate.
Limited within narrow rangesof wattage by lamp size, socketstyle, and ballast compatibility.
Screw-in lamps substitute for eachother and for most incandescentlamps, except where they aretoo large to fit. Cannot be usedin dimming fixtures. Othercompact lamps have specializedbases that limit substitution.
Color RenderingIndex (CRI)
100 100 50 to 95 60 to 85
Effect of emperatureon Light Output
Minimal. Minimal.
Serious loss of light
output above and belowoptimum lamp temperature(about 38°C).
Serious loss of Eight output above andbelow optimum lamp temperature(about 38°C). Lamps that use mercuryamalgam maintain light outputmuch better at low temperatures.
Starting Interval Instantaneous. Instantaneous.
Instantaneous for lamps withInstant-start ballasts. Aboutone second for rapid-startballasts. One to severalseconds for preheat ballasts.
One to several seconds. Units withmercury amalgam require about oneminute to reach full brightness.
Control of LightDistribution
Some styles allow verytight focussing.
Some styles allow verytight focussing.
Allows only loosefocussing. Most controlperpendicular to lamp axis.
Allows moderately tightfocussing, especially withunconventionally large fixtures.
Acoustical Noise Minimal. Minimal.
All magnetic ballasts producesome noise, and defectivenoisy units are fairly common.Some electronic ballastshave noticeable noise.
Good units are quiet, cheapunits may be noisy.
Power Factor No problem. No problem.Ballasts with high power factorare available. Some ballastshave low power factor.
Units with high power factor areavailable. Some have low power factor.
Harmonic Distortion None. None.
High distortion occurs
primarily In cheaperelectronic ballasts.
All units with electronic ballasts
have significant harmonicdistortion. Cheaper units havemuch more than others.
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Mercury
Vapor
Metal
Halide
High-Pressure
Sodium
Low-Pressure
Sodium
0 to 60,000 4,000 to 160,000 2,000 to 50,000 1,800 to 35,000
o 45 30 to 45 25 to 35
00 5,000 to 20,000 10,000 to 24,000 18,000
o 65 70 to 130 50 to 150 100 to 190
rge lamps) to 50 (small lamps) 7 (large lamps) to 30 (small lamps) 10 (large lamps) to 35 (small lamps) ca. 20
titutions within type highly limitedallast compatibility. Some mercuryr lamps substitute for incandescent
ps without external ballasts, but theseminimal efficacy advantage.
Substitutions within type highlylimited by ballast compatibility.
Substitutions within type highly limited byballast compatibility. Some HPS lamps aredesigned as direct substitutes for mercury vaporlamps, offering major efficacy improvement but worse color rendering than other HPS lamps.
Substitutions withintype highly limited byballast compatibilityand specialized sockets.
o 50 60 to 70 20 to 85 0 to 20
imal loss of output above -29°C. Minimal loss of output above -29°C. Minimal loss of output above -29°C. Minimal loss ofoutput above -29°C.
8 minutes 3 to 10 minutes 5 to 10 minutes 7 to 15 minutes
ws moderately tight focussing. Allows moderately tight focussing. Allows moderately tight focussing.
Allows only loosefocussing. Mostcontrol perpendicularto lamp axis.
asts are magnetic, andduce some noise.
Ballasts are magnetic, andproduce some noise.
Ballasts are magnetic, and produce some noise.Ballasts are magnetic,and producesome noise.
asts with high power factor are available.e ballasts have low power factor.
Ballasts with high power factorare available. Some ballastshave low power factor.
Ballasts with-high power factor are available.Some ballasts have low power factor.
Ballasts with highpower factor areavailable. Some ballastshave low power factor.
or, assuming that thests are magnetic. Minor, assuming that theballasts are magnetic. Minor, assuming that the ballasts are magnetic.
Minor, assuming
that the ballastsare magnetic.
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Maximum lighting power requirementsare also included for exit signs andexterior building grounds lighting[ECBC 7.2.2 and 7.2.3]. As per ECBC, for Exterior Grounds
Lighting luminaires greater than 100 Watts shall have a minimum efficacy of60 Lumens/Watt, unless controlled with
a motion sensor. As shown in Fig. 9,luminaires meeting these requirementsinclude fluorescent, mercury vapor andhigh pressure sodium.
Prescriptive RequirementsFor meeting Interior Lighting Powerrequirements, [ECBC 7.3], the installedinterior lighting power is first calculatedtaking into account all the luminairesincluding lamps, ballasts, currentregulators, and control devices proposed tobe installed in the building. Compliancecan then be achieved by the Building
Area Method [ECBC 7.3.2] or the SpaceFunction Method [ECBC 7.3.3]. Boththe methods compare installed lightingpower (Watts) as proposed in the building
with maximum allowed lighting powerallowance (Watts) calculated based on thevalues of Lighting Power Densities (LPDin W/m2) given in able 7.1 and able 7.2of ECBC respectively. Sample LPD valuesare given in able 3.
Building Area Method For easier understanding consider theproposed building is an exclusive one‘building area type’ (such as office).
Step 1: Depending upon the typeof the proposed building, select thecorresponding permissible LPD fromable 7.1 of ECBC.
Step 2: Determine the gross lightedfloor area of the building.
Step 3: Calculate the interior lightingpower allowance (LPA) which is theproduct of the gross lighted floor area
ECBC Compliant Lighting
Design Strategy
Many things can go wrong with thebuilding lighting system and well-intentioned attempts to make it energyefficient. Critical missteps to watch outfor include:
• Specifying the amount of light forgeneral usage without considering theneeds of specific tasks (for example,supplying light for general office workbut not addressing the effect of glareon computer screens);
• Designing a daylighting strategy butnot enabling the lighting system todim or turn off when there is sufficientdaylight in the interior space;
• Supplying inadequate control oflighting by not allowing lights to beadjusted to specific needs (i.e. turnedon in groups or “banks”, or dimmed),and not providing easily accessiblecontrol switches;
• Adding a large window area to thefaçade for daylighting but ignoringthe problems of solar heat gain and theneed for shading;
• Designing/sizing the building’s HVACsystem on rules of thumb and notaccounting for the reduction in coolingloads created through efficient lighting
system.
Compliance Approaches - GeneralECBC sets mandatory and prescriptiverequirements for lighting power densityand lighting controls. Compliance withprescriptive requirements can be shownthrough the Building Area Method orthe Space Function Method. In bothcases, mandatory lighting requirementsare still applicable.
Mandatory RequirementsLighting Control—Astronomical imersand occupancy sensors are required toautomatically turn lights off in mostenclosed interior spaces [ECBC 7.2.1.1].Control devices also required to override anautomatic shutoff control (either manuallyor through an occupancy sensor) [ECBC7.2.1.2]. If Daylighting strategy is used inthe design, ECBC requires controls that canreduce the light output of luminaires in thedaylit space, by at least half [ECBC 7.2.1.3].
Tere are also control requirements
for exterior lighting (with photosensoror time switches) and specialty lightingapplications (i.e. displays, hotel rooms, tasklighting) [ECBC 7.2.1.4 and 7.2.1.5].
and the selected LPD for the building.(Gross Lighted Floor Area X LPD)
Step 4: Calculate the total installedlighting power (ILP) of the all proposedluminaires in the building (in accordance
with ECBC 7.3.4.1)
Step 5: Compare ILP values with LPAvalues. If ILP is less than or equal toLPA, the lighting system of the buildingcomplies with ECBC. Otherwise, it isnot.
Space Function Method
Step 1: Looking into the listed spacefunction heads/sub-heads given inthe able 7.2, identify various spacefunct ions (enclosed by partitions 80% orgreater than ceiling height) as applicablein the proposed building (for instance,hospital building which has number ofsub-heads), and also determine theircorresponding LPDs f rom the able.
Step 2: Determine the gross lightedfloor area of each of the identified spacefunction heads/sub-heads (as guided inECBC under 7.3.3 b).
Step 3: Calculate the interior lightingpower allowance (LPA) which is the sum
of the product of the gross lighted floorarea under each of space function head/sub-head and the corresponding LPD ofeach.
Step 4: Calculate the total installedlighting power (ILP) of the all theproposed luminaires in the building (inaccordance with ECBC 7.3.4.1).
Step 5: Compare ILP values with LPAvalues. If ILP is less than or equal to
LPA, the lighting system of the buildingcomplies with ECBC. Otherwise, it isnot.
Table 3: Sample LPD Values (max. permissible) as per ECBC
Building Area
Method
LPD
(Watts/m2)
Space Function
Method
LPD
(Watts/m2)
Office 10.8 Office Enclosed/Open Plan 11.8
Library 14.0 Classroom/Lecture/ raining 15.1
Retail/Mall 16.1 Family Dinning 22.6
Cafeteria/ Fast Food 15.1 Hospital (Emergency) 29.1
Parking Garage 3.2 Corridor/ransition 5.4
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o complete the zonal cavity calcu lation,three fundamental quantities must beknown: the Room Cavity Ratio (RCR),the Coeff icient of Utilizat ion (CU), andthe Light Loss Factors (LLF).
Room Cavity Ratio: Room Cavity Ratio(RCR) characterizes a room by shapeand is calculated using the formulabelow, using the room dimensions andlight fixture distance over the working
desk. Refer Figure 10, as an examplefor sample calculation of RCR as shownbelow:
Coefficient of Utilization: CU is ameasure of the fixture’s ability to distributelight down to the work plane using the RCR
4.55(10-2.5-1.5) (2 0+10)= = 20 X 10
5(H) (L+W)
L X W =RCR
Exterior Lighting Power requirements[ECBC 7.3.5] require calculating theconnected lighting power for buildingentrances, exits, and facades. hesemust be below the power limits listedin ECBC for each lighting application.Figure 9 suggests specific technologiesfor exterior ground lighting.
Basic Light Design Concept
When designing or retrofitting the
lighting, the general illuminance, oramount of light that reaches a surface, canbe assessed through manual ca lculations.Te Illuminating Engineering Society ofNorth America (IESNA) has establisheda procedure for determining how muchilluminance is needed for a given task. Te
Zonal Cavity or Lumen Method (Source:E Source echnology Series-LightingVol. I) described below considers severalfactors to determine type and numberof fixtures that would be appropriate to
meet the illuminance requirements ofthe space.
Zonal Cavity Method: he basicformula used in this method springfrom the definition of illuminance: 1foot-candle (fc) = 1 lm/ft2. hat is, tomaintain an average of 40 fc in an areaof 100 ft2, one needs 40 x 100 = 4,000 lmcoming out of the fixtures. But severalmodifying factors must be considered:he fixture is not absolutely efficientin dispensing light; much of that light
may be lost while being reflected off ofvarious surfaces before it arrives at the
work surface. A lso, l ight source s degrade with age and dir t buildup.
value and the surface reflectance of the walls, floor, and ceiling. Fixture efficiencyis the proportion of lamp light that escapesthe fixture at any angle, whereas CU isthe proportion of lamp light that reachesthe work plane. Te two are calculateddifferently and are not interchangeable. Allelse being equal, a fixture in a room with a
low RCR will have a higher coefficient ofutilization than if it were in a room witha high RCR. CU values are given by thefixture manufacturer.
able 4 shows how rapidly the CUvalue drops as wall reflectance decreasesor as RCR increases.
Table 4: Typical Coefficient of
Utilization (CU) Values
Reflectance
(Wall)50 30 10
Reflectance
(Ceiling)80 50 80 50 80 50
1 67 56 65 53 53 51
2 66 54 63 51 51 49
3 65 52 61 50 50 48
4 64 50 59 48 48 46
5 63 48 57 46 46 44
6 61 46 53 44 44 42
7 59 43 51 42 42 40
8 56 41 49 40 40 38
9 54 40 47 38 38 36
10 51 39 45 36 36 34
Light Loss Factor: Light distributionis not only affected by the color andreflectance of room surfaces andfurnishings but also by change inlighting output over time, which isprincipally a function of lamp lumendepreciation and fixture dirt buildup.Lumen depreciation data can be foundin technical information suppliedby the lamp manufacturer, and dirt
depreciation values can be taken fromgraphs (IESNA) for various types offixtures and dirt environments.
Once these Light Loss Factors have beentaken into account, one has a more realisticpicture of the “maintained foot-candlelevel.” Te number of lamps (or fixtures)needed to attain that sustained minimumlight level over a lamp’s lifetime can thenbe determined by the zonal cavity formula:
Tis method is heavily dependent onseveral assumptions: that surface reluctancesare reasonably accurate, the fixtures are
L=20ft
Fixture hangs below
ceiling 1.5ft H-6 ft
Task height=2.5 ft
Desk
Desk
W=10ft
ig 10: Example for Room Dimensions,
lacement of Lighting Fixture, and RCR
alculation
Source: E Source Lighting Atlas)
10ft
140
120
100
80
60
40
20
0
100 200 300 400 500 600 700 800 900 1000
S y s t e m E ffi
c a c y ( L u m e n s / W a t t )
System watts
High Pressure Sodium
Metal Halides
System Efficiency < 60 lm/W not allowed per ECBC unless controlled by a mo-
tion sensor
Fluorescent
Incandescent
Fig 9: Exterior Grounds Lighting and specific Technologies
(Source: Adapted from ASHRAE/ IESNA Standard 90.1-1999)
R o o m C
C a v i t y R a t i o ( R C R )
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reflectance. Avoid furniture colors andplacement that will interfere with lightdistribution. Keep ceilings and walls asbright as possible.
Avoid glareInability to control glare is the mostcommon failure in incorporatingdaylighting and especially important
where computer use is extensive. Bestpractice gla re control includes the use ofadjustable blinds, interior light shelves,fixed translucent exterior shadingdevices, interior and exterior fins, andlouvers.
Control Daylight strategies do not save energy
unless electric lights are turned offor dimmed appropriately. ECBCrequires controls in daylit areas thatare capable of reducing the light outputfrom luminaire s by at least half. It isimportant to have properly functioningcontrols that are placed in appropriatelocations and are calibrated to providea consistent level of lighting. Goodlighting design is critical for an energy-efficient and comfortable building.• Install effective placards at lighting
controls;• Install dimmers to take advantage of
daylighting and where cost-effective;• Replace rheostat dimmers with efficient
electronic dimmers;• Combine time switching with
daylighting using astronomicaltimeclocks;
• Control exterior lighting withphotocontrols where lighting can beturned off after a fixed interval.
Design Tips
Many offices that were designed tohandle typing and similar horizontaloffice tasks earlier are now filled with
evenly distributed in the room; and otherconcerns such as voltage, room temperature,fixture temperature, and ballast factor arenormal and will not affect lamp lumenoutput. Te basic RCR calculation assumesthat the fixtures are mounted on the ceiling;variations in the RCR calculation methodcan account for direct/indirect fixtures
mounted on pendants.Te above discussion pertains to casesinvolving uniform light levels. In somecases, non-uniform levels are better, even ifexisting levels are uniform. Tis typicallyoccurs in merchandising, where one would
want products to stand out.
Tips for Energy Efficient
Lighting
Any lighting system generates heat thatneeds to be dissipated . By designing anenergy efficient lighting system that in-tegrates daylighting and good controls,heat gains can be reduced significantly.his can reduce the size of the HVACsystem resulting in first-cost savings.
Daylighting Tips
Daylighting benefits go beyond energysavings and power reduction. Daylightspaces have been shown to improve people’sability to perform visual tasks, increase
productivity and reduce absenteeismand illness. Building fenestration shouldbe designed to optimize daylighting andreduce the need for electric lighting.Following tips can help in designing anintegrated lighting system:
Coordinate with design of electriclights;• Plan the layout of interior spaces—
use the layout to allow daylight topenetrate far into the building (Fig.
11).• Orient the building to minimize
building exposure to the ea st and westand maximize glazing on the southand north exposures.
• Follow ECBC Visible Lightransmittance (VL) requirements[ECBC 4.3.3.1] for windows—tomaximize light and visual quality.
Effective daylighting strategy shouldinclude a combination of the following:
Address interior color schemes;
Interior surfaces, and especiallythe ceiling, must be light colored.Consider light colored furniture androom partitions to optimize light
desktop computers and workstations(often having reflective surfaces), whichrequire careful consideration of bothhorizontal and vertical illumination inthe offices.• Deal with each activity area and each
fixture individually;• Eliminate excessive lighting by reducing
the total lamp wattage in each activityarea;• Lighting layout should use task lighting
principle. Install focussing lamps orflexible extensions wherever needed;
• Plan for future changes in activitiesand space layout. Install fixtures andcombinations of fixtures that provideefficient lighting for all modes of spaceusage.
• While selecting recessed lightingfixtures, one must evaluate the reductionin lamp life as a result of higher junctiontemperature (Fig. 12).
Simulation Tips in Lighting DesignSimulation using a variety of computersoftware tools is not only the way adesign professional or team determinescompliance with the ECBC, but itmay be the best method for guiding adesign using a system-based approach.Lighting software helps users comparelighting alternatives and make sure thatthe ultimate design choice will provide
quality light. A wide range of variables—different light sources, fixtures of varyingefficiency and photometric, daylighting,and rooms with a wide range ofgeometries and surface finishes—allmake lighting design a challenge worthyof computer modeling.
In order to be useful, the mostsophisticated software tools requiretraining and experience on the part of theuser, but numerous simpler programs arealso available for the designer who doesnot need all the functionality of the most
complex products. A number of lightingsoftware tools are also available free ofcharge. Tey come from governmentagencies and private companies, and they
Top Li ghti ng
Clear acrylic
glazing
Light Shelf
Side Lighting
White translucent acrylic glazing
he schematic shows a mix o top-lighting , side-lighting, light shelves, high re lectance ceilings and
wal l di usio n to p rovi de a irl y un ior m dee p-pl andaylighting without the glare o direct sunlight.
Fig 11: Simple daylighting Techniques
(Source: E Source Lighting Atlas)
R2=0.96
T- point Temperature (deg c)
50000
40000
30000
20000
10000
0
35 40 45 50 55 60
L i f e ( h r s )
ig 12: Effect of Junction Temperature
n Life of LED Lamp
Source: Lighting Research Institute)
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• Replace ballasts with high efficiencyor reduced wattage types, or upgradeballasts and lamp together;
• Relocate or reorient fixtures to improvevisual quality;
• Modify existing fixtures to reduce/eliminate light trapping and/or improvelight distribution. In fixtures having
shades that absorbs light, modify oreliminate the shade;
able 5 provides an overview oflighting design tools used by the lightingprofessionals.
Lighting Retrofit Tips• Replace incandescent and other
inefficient lamps with lamps withhigher lighting efficacy;
•
Eliminate excessive lighting; disconnectthe ballast or remove the fixture wherethey are not needed;
offer a wide range of capabilities. Moreinformation about lighting softwareis available from the Building EnergySoftware ools Directory maintainedon the U.S. Department of Energy
Web site. In addition, Te IlluminatingEngineering Society of North Americaperiodically conducts a survey of lighting
software tools and publishes the resultsin its magazine Lighting Design and Application (LD+A).
Table 5: Commonly Used Lighting Design Software
Software Discription Contact Information
AGI32Lighting calculation and visualization program. Latest release, 1.7, addsdaylight factor calculations, unified glare-rating calculations for discomfortglare in interiors. Company also offers a simplified version, AGI-Light.
Lighting Analysts Inc. Littleton,Colorado, USA Phone: +1-303-972-8852E-mail: [email protected]: www.lightinganalystsinc.com
Autodesk VIZ Tree-dimensional modeling, rendering, and presentationcapabilities. Includes daylighting calculations.
Autodesk Inc.San Rafael, California, USA Phone: +1-800-440-4198URL: www.autodesk.com
Building Design Advisor
A data manager and process controller that allows building designers touse several analysis and visualization tools throughout the building designprocess. Te current version includes links to a simplified DaylightingComputation Module (DCM), a simplified Electric lighting ComputationModule (ECM), and the DOE-2.1E Building Energy Simulation software.
Konstantinos PapamichaelLawrence Berkeley NationalLaboratory Berkeley, California Phone: +1-510-486-6854E-mail: [email protected] URL: http://gaia.lbl.gov/
DAYSIM
Daylighting analysis software that predicts the annual daylight availabilityand electric lighting use in buildings that use manual and automated lightingand blind controls. Based on Radiance software and available for free.
Christoph ReinhartNational Research Council Canada Institute for Research in ConstructionOttawa, Ontario Canada Phone: +1-613-993-9703E-mail [email protected] URL: www.daysim.com
DIALux Lighting calculations and modeling from DIAL, a Europeanlighting services organization that is supported by manufacturers.Useful for simple calculations and available for free.
DIAL GmbH
Lüdenscheid Germany Phone: +49-0-2351-10-64-360E-mail: [email protected]: www.dial.de
LIE-PROLightin g design tool from Hubbell Lighting Co. Includesindoor and outdoor lighting capabilities and rendering.
Columbia Lighting, Spokane, Washington, USA Phone: +1-509-924-7000E-mail [email protected]: www.columbialighting.com/litepro/features.htm
Lumen Designer
Te latest upgrade of the popular Lumen Micro product. Adds internalmodeling and daylighting capabilities. A highly interactive interfacefeatures a Design Wizard for setting up complex projects. Productalso includes plug-ins for roadway lighting and advanced rendering.Company offers a simplified version: Simply Lighting 2002.
Lighting echnologies Inc.Denver, Colorado, USA Phone: +1-720-891-0030URL: www.lighting-technologies.com
ProjectKalc
Helps the user compare the energy and operating cost impacts of alternativelighting upgrade solutions. It can handle lighting upgrades involving controls,relamping, delamping, tandem wiring, and more. It includes user-modifiabledatabases of costs, labor time, and performance for over 8,000 commonhardware applications. Te software is available free of charge through theU.S. Environmental Protection Agency (EPA) Energy Star program.
EPA Energy Star Program, Washington, D.C., USA URL: www.energystar.gov/index.cfm?c=business.bus_projectkalc
Radiance
An advanced lighting simulation and rendering package that calculatesspectral radiance values and spectral irradiance for interior and exterior spacesconsidering electric lighting, daylight, and inter reflection. Used by architectsand designers to predict illumination, visual quality, and appearance ofdesign spaces. Used by researchers to evaluate new lighting and daylightingtechnologies and study visual comfort and similar qualities related to the visualenvironment. It is available for free. Tere is a project underway to develop anice interface to this extremely powerful application to improve its usability.
Charles EhrlichLawrence Berkeley National LaboratoryBerkeley, California, USA Phone: 510-486-7916E-mail: [email protected] URL: http://radsite.lbl.gov/radiance/HOME.htmlFree
Visual Lighting analysis software for interior and exterior applications. Integratesanadvanced 3-D modeling environment with an intuitive interface. Professionalpresentation capabilities enable user to quickly develop, analyze, and modifyadvanced lighting designs. Basic version is available free of charge.
Acuity Brands Lighting Visual Support Center, Conyers, Georgia, USA Phone: 800-279-8043E-mai: [email protected]: www.visuallightsoftware.com
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Developed by USAID ECO-III Project eam:
echnical Contents: Satish Kumar, Ravi Kapoor,
and Anurag Bajpai
Editing: Ravi Kapoor
Layout Design: Meetu Sharma
For more information:
Dr. Ajay Mathur, BEE ([email protected])
Dr. Archana Walia, USAID ([email protected])
Mr. Aalok Deshmukh, ECO-III Project([email protected])
Version 2.0- March 2011 ECBC Tip Sheet > Lighting 12
the less likely it is that sensors will bedisabled, disconnected, or bypassed.he following provides a strategy forselecting the right controls for buildings.
Define Application Goalshe first step in determining the rightcontrol strategy is to thoroughly define
and understand the application goals.Lighting designers should be asked toprovide iso-lux charts which discuss theillumination level in the space (Fig. 13).
Switching or Dimming he first primary decision after definingthe load and the application goals is
whether to switch or dim the load.Switching and dimming are stand-alone strategies but are often used inthe same facility, and may be integratedin the same control system. Dimmingcapability should always be incorporatedinto areas where daylighting is theprimary lighting approach. When usingphoto sensors in a dimming strategy,it is important to properly commissionand calibrate it. Failure to do so cansometimes result in more energy use.
Degree of Automation Needed It is worthwhile to determine theamount of local vs. centra l control that isneeded from the lighting control system.
Manual lighting controls range from asingle switch to a bank of switches anddimmers that are actuated by toggles,rotary knobs, push buttons, remotecontrol, and other means. Manual
controls can be cost-effective optionsfor small-scale situations. However, asthe lighting system grows, automatedsystems become more cost-effective andare better at controlling light . Manualcontrols often waste energy becausethe decision to shut off the lights whenthey are not needed is based entirely on
human initiative.
References:
Book References:1. E Source (2005): E Source echnology
Atlas Series - Volume I: Lighting,Boulder, CO, USA
2. Energy Efficiency Manual, by DonaldR. Wulfingoff, Energy Institute Press.
3. Energy Conservation Building Code,Ministry of Power, May 2007.
Web References:1. Illuminating Engineering Society of
North America (IESNA),http://ww.iesna.org
2. Advanced Buildings: echnologiesand Practices,http://www.advancedbuildings.org/
3. he Lighting Research Center atRensselaer Polytechnic Institute,http://www.lrc.rpi.edu/
4. Heshong-Ma one Grouphttp://www.h-m-g.com/
5. he New Buildings Institute,
http://www.newbuildings.org/light-ing.htm
6. Windows and Daylighting , LawrenceBerkeley National Laboratory,http://windows.lbl.gov/
Maintenance TipsTere are important considerations thatneed to be made to optimize a design forenergy efficiency in lighting: reductionin first costs, reduced operation andmaintenance, and increased occupantproductivity and comfort. Consider thefollowing:•
Good lighting also effects the operationand maintenance of a building. Asimpler and easy to control lightingsystem will lower the “first cost” of thesystem.
• Fluorescent lamps last an average of10 times longer than incandescent andreduce re-lamping labor costs.
• Clean fixtures and lamps at appropriateintervals to maintain optimum lightingoutput.
Lighting Controls TipsPurpose of Lighting Controls: In manyapplications, the overall purpose of thelighting control system is to eliminate
waste while providing a product ivevisual environment. his may entail:1. providing the right amount of light;2. providing light where it’s needed.
A few issues to keep in mind whi ledesigning controls are:• Install a separate control circuit for
each lighting element that operates on a
distinct schedule;• Where light fixtures are needed in a
predictable variety of patterns, installprogrammable switches;
• Install lighting controls at visible,accessible locations;
• Where lighting is needed on a repetitiveschedule, use timeclock control;
• Install occupancy sensors in bathrooms,conference rooms, and other spaces notin constant use.
Controls, switches, shades, timers,and other lighting strategies canget complicated. It is likely thatadjustments will occur after occupancy.he easier the lighting system is tounderstand and adjust to accommodatethe occupants and building function,
Align control circuits parallel to daylight
contours when daylight levels vary across the
space. In these plans and section o a sidelit
oice and skylit actor y, “A” experiences the
most daylight and is turned o or dimmed
irst, “B” is controlled second, “C” receives
the least daylight and is let at ull power tomaintain wal l brightness. he oice pendent
direct-indirect luminaires are dimmed in
response to daylight.
B C C
C
B
A
B
A
C
A
800Lux 600Lux 400Lux 200Lux
Fig. 13: Plan Views of Daylight Isolux Contours
(Source: Adapted from Advanced Lighting Guidelines, New Buildings Institute)